Carbon offsetting schemes not so green

Coldplay hoped mango trees would offset pollution

By Jasper Copping

12:01AM BST 19 Aug 2007

As millions of Britons jet off to foreign climes for their holiday this month, the more environmentally minded travellers will have salved their consciences by paying for trees to be planted to compensate for the carbon emissions caused by their flight.

But a ground-breaking study has now called into question the effectiveness of using trees to "offset" emissions, suggesting that their ability to "lock-up" carbon dioxide has been greatly exaggerated.

Forests have long been seen as an effective way of absorbing the greenhouse gases, such as carbon dioxide, which are thought to trap the sun's heat in the atmosphere, causing global warming.

Celebrities, including the Rolling Stones and Leonardo DiCaprio, the film actor, have signed up to schemes to plant trees to offset their own emissions.

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However, the new research found that trees bathed in extra carbon dioxide grew more tissue, but did not necessarily store significant extra quantities of carbon. Instead, the tree's capacity to absorb the gas depended on water and nutrient levels.

The news will come as a blow to the carbon-offsetting industry, which has expanded rapidly as individuals and companies try to atone for their carbon dioxide emissions by paying companies to plant trees for them.

In 2003, the Rolling Stones held a "carbon neutral" tour, planting one tree for every 60 tickets sold.

Dido, the singer, and even the celebrity drinking club, the -Groucho, are all reported to have paid out for trees to be planted.

In 2002, Coldplay, the band fronted by Chris Martin, the husband of actress Gwyneth Paltrow, announced it would offset the environmental impact caused by the release of its second album, A Rush of Blood to the Head, by planting 10,000 mango trees in southern India. By last year many of the trees had died.

David Cameron, the Conservative Party leader, also says he pays into offsetting schemes for all his flights, road and rail trips, and a growing number of blue chip companies and airlines, as well as Government departments, now sign up to such projects.

According to the Department for Environment, Food and Rural Affairs, Britons spent £60 million on such schemes last year. This is forecast to grow to £250 million annually by 2009.

The latest findings come from an ongoing study - known as the Free Air Carbon Enrichment project - which has been running for 13 years at Duke University, North Carolina, in the US.

Researchers bathed plots of pine trees in extra carbon dioxide every day for 10 years and found that while the trees grew more tissue, only those that received the most water and nutrients stored enough carbon dioxide to offset the effects of global warming.

Ram Oren, the ecologist who led the project, said the research suggested that planting more trees would not be successful in slowing the pace of climate change. "More trees don't necessarily mean less carbon dioxide," he said. "Planting trees is not going to do a whole lot to decreasing carbon concentration.

"What we're finding is that extra carbon very quickly goes back into the atmosphere if there are low nutrients and water available.

"And we are not going to be able to increase the capacity of forests to hold carbon, because we couldn't fertilise such large areas or provide sufficient water. It would cause such pollution that the consequence would be much worse than carbon dioxide enrichment in the atmosphere."

But Ru Hartwell, the director of Treeflights, an offsetting company planting trees in Wales and Peru, said: "There are problems with tree planting but it is only one way in which we are going to get on top of the problems of global warming. I have complete faith that tree planting is positive and we should not just chuck away our spades and do nothing."